More recently used to unintentionally irritate people who prefer straight forward answers. Literally, "something is urgently wrong but instead of me just immediately telling you, you must figure it out yourself in the amount of time it takes me to make this sarcastic and unhelpful remark."

Can be typed as well.

Example, this used to be proper protocol in an urgent situation--
Bob: "Joe, watch out for that large pothole you seem to be unknowingly driving into."
Joe: (avoiding pothole) “Thank you for your timely and straight-forward warning. I appreciate you using the first sentence after you were alerted to this danger to tell me about this pothole, instead of uttering a one-worded, useless phrase.”

The Urban Dictionary T-Shirt

In conversation, a word that announces one's contempt for and hostility toward the person they're about to contradict. Most common on the Internet, for obvious reasons.

Person 1: The first movie I ever saw in the theater was "Empire Strikes Back." Man, that was intense for a 6-year-old, so much larger than life. And when Darth Vader said "Luke, I am your father," I was freaking out. I'll never forget that day.